Nigerian Journal of Tropical Engineering
Vol. 16 No. 1 |ISSN: 1595-5397| Dec. 2022
Jauro M. S. et al
DOI: 10.59081/njte.16.1.006
INFLUENCE OF DIGESTION TEMPERATURE ON
BIOGAS PRODUCTION FROM DISCARDED CASSAVA
(manihot esculenta) PEELS
Jauro, M. S.1*, Aliyu, B.2, Abubakar, A. J.2 and Umar, A.3
1
2
Department of Agricultural Engineering, College of Agriculture Jalingo, Taraba State. Nigeria
Department of Agricultural and Environmental Engineering, Modibbo Adama University, Yola,
Adamawa State. Nigeria
3
Department of Electrical and Electronics Engineering, School of Engineering. Federal
Polytechnic Bali, P. M. B. 005 Taraba State. Nigeria
*Corresponding author: msjauro2020@yahoo.com, +2348062992302
Abstract
Anaerobic digestion is an established technology for treating different kinds of wastes and to
simultaneously produce biogas (mixture of methane and carbon dioxide), which is useful and
renewable energy source. In this work, the influence of temperature on the biogas production
from cassava peels was studied in batch type anaerobic digesters of volume 500 ml at digestion
temperatures of 35±50C, 45±50C and 55±50C for a retention period of 30 days. The quantity of
the biogas produced daily were measured with a pressure gauge for the 30 days retention period
and converted to volumetric gas yield. It was observed that the cumulative biogas yield increases
by 25 % when the digestion temperature was raised from the mesophilic temperature range to
thermophilic temperature range. The highest cumulative biogas yield of 289.33 × 10−5 m3/kgTS was obtained with the highest digestion temperature of 55±50C. It is therefore concluded that
biogas production increases with the increase in digestion temperature and it is recommended
that anaerobic digestion should be carried out at the thermophilic temperature range for better
gas yield.
Keywords: Biogas, digestion temperature, cassava peels, mesophilic, thermophilic
1.0
Introduction
Cassava is one of the most important
communities (David and Tope, 2018; Ubalua,
agricultural food crops in Southern and
2007).
Western Nigeria. Several varieties of products
such as starch, gari, cassava flour, and fufu are
Macias-Corral et. al. (2008) and Olaniyan et.
among the staple food of the people of the
al. (2017) reported that agricultural wastes
southern, western and some part of northern
such as cassava peels are amid the major
Nigeria which are the products of cassava
environmental challenges in both developed
(Lebot, 2009; Odediran et. al., 2015). During
and underdeveloped nations. The effect of
the conversion of cassava into these products,
such wastes on natural resources such as
large quantity of waste such as cassava peels,
surface and ground waters, soil and crops, as
slurry etcetera are generated which are mostly
well as human health are enormous as they
dumped with in the community constituting a
constitute to environmental hazards, leading to
major problem to the inhabitants of those
global warming and causing environmental
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Vol. 16 No. 1 |ISSN: 1595-5397| Dec. 2022
Jauro M. S. et al
diseases thereby resulting in high mortality
rate among populace (Olaniyan et. al., 2017;
Sarmah, 2009). But the agricultural wastes
such as the cassava peels and other waste have
been reported to possess huge potentials for
alternative energy source from fire wood and
fossil fuels during anaerobic fermentation
(Sammy et. al., 2018). Anaerobic fermentation
significantly reduces the total mass of wastes
generated to liquid fertilizers and produces
energy (Navickas and Venslauskas, 2012;
Vindis and Mursec, 2009). The anaerobic
fermentation
can
take
place
under
psychrophilic condition (16 ºC – 25 ºC, e.g. in
landfills, swamps or sediments), mesophilic
condition (35 ºC – 40ºC, e.g. in the rumen and
anaerobic digesters) or thermophilic condition
(52 ºC – 60 ºC, e.g. in anaerobic digesters or
geo-thermally heated ecosystems) (Kestutis et.
al., 2013). Kestutis et. al. (2013) reported that
the optimum digester temperature setting,
considering both the potential biogas yield and
energy value, is one of the most critical factors
for the economically viable digester operation.
DOI: 10.59081/njte.16.1.006
substrate, hence increases the rate of
transfer of liquid towards gas due to the
low solubility of the gas, reduction in
the liquid viscosity resulting in the
reduction of the energy required for
agitation as well as improves the
separation of liquid-solid biomass.
4. Particularly increase the death rate of the
pathogenic bacteria, which decreases the
time necessary for their reduction.
Moreover, the reactions of oxidations of
organic acid become more energetic at high
temperature, which is advantageous for the
degradation of fatty acid to long chain fatty
acid, and other intermediaries (Chynoweth et.
al., 1993, 1994). Temperature is significantly
an important factor in anaerobic digestion
(AD) as its affects the rate of the reaction.
Prakasha et. al., (2015) reported that digestion
temperature has strong influence on quality
and quantity of biogas produced. Mackie and
Bryant (1995) found that thermophilic (60°C)
anaerobic digestion of cattle waste is more
stable as compared to mesophilic (40°C) and
reported that thermophilic digestion is 4
(Four) times more effective and can yield
more biogas. Hassib et. al. (2004) compared
the performance of the anaerobic digestion of
fruits and vegetable wastes in thermophilic
(55°C) digester with those in psychrophilic
(20°C) and mesophilic (35°C) digesters. The
study showed that biogas production in
thermophilic digesters was higher than those
in psychrophilic and mesophilic digesters by
144 and 41% respectively. During the codigestion of waste activated sludge Gou et. al.
(2014) found that the average gas production
rate of the thermophilic (55°C ) condition was
1.6 times higher than that of mesophilic
(35°C) condition and Manjula and Mahanti
(2014) reported that biogas production
increases with increase in temperature as was
observed during the co-digestion of
Lignocellulosic biomasses with cattle dung at
various temperature ranges. The objective of
Digestion temperature has been reported to
have direct effect on the physicochemical
properties of all the components in the
digester and also affects the thermodynamics
and the kinetics of the biological processes.
The temperature determines if a specific
reaction is favourable (Kestutis et. al., 2013).
According to Hansson et. al. (2002) the
increase in the temperature has the following
advantages:
1. Increase the solubility of the organic
compounds which makes them more
accessible to the micro-organisms.
2. Increase the chemical and Biological
reaction rates and hence accelerates the
conversion process, therefore the reactor
can be smaller and can operate with a
shorter hydraulic retention time (HRT)
3. Improves
several
physicochemical
properties like diffusivity of the soluble
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Nigerian Journal of Tropical Engineering
Vol. 16 No. 1 |ISSN: 1595-5397| Dec. 2022
Jauro M. S. et al
this study is to investigate the effect of
temperature on biogas production rate from
Cassava peels mixed with cattle dung.
DOI: 10.59081/njte.16.1.006
The bio-digesters were made using 500 ml
rani bottles. The mass of the substrates as well
as the inoculum were measured using digital
weighing balance. Water bath were used to
obtain a temperature controlled environment.
Water heater was used to heat water that was
added to the water bath when the temperature
goes down. Mercury in glass thermometers
were used for measuring the temperature of
the water in the water bath and Pressure gauge
was used for measuring the pressure of the
gas.
2.0
Materials and Method
2.1
Materials Used
The substrate (Dicarded cassava peels) were
obtained from cassava processing companies
locally from four local government areas
(Gassol, Ardo-kola, Bali and Jalingo) of
Taraba state, which are the major cassava
producers in the state. Parts of the collected
cassava peels were cleaned and sun dried in
the area and later ground into smaller pieces
using mortar and pestle and kept for
experiment, while the other parts was oven
dried and pounded for proximate and chemical
analysis. Fresh cow dung was obtained as
inoculums from animal farm at College of
Agriculture Jalingo, Taraba state Nigeria. The
Physico-chemical analysis of the Cassava
Peels was carried out at the National Research
Institute for Chemical Technology (NARICT)
Zaria, Kaduna state Nigeria from where the
following were determined: Moisture Content,
Total Solid, Volatile Solid, biochemical
oxygen demand (BOD), Crude Lipid, Crude
Fibre, Nitrogen content, Crude Protein, total
solid concentration, ion content, mineral
content and volatile fatty acid content. The
above were determined using standard
methods as described by AOAC (1990); Asam
et. al. (2011); Jagadish et. al. (2012) and
Onyeike and Osuji (2003). Atomic Absorption
Spectrophotometer (AAS) Machine was used
to determine the ion and mineral contents
while volatile fatty acid contents were
determined using Gas chromatography-mass
spectrometry (GC-MS) machine. The average
total solid and carbon-nitrogen (C:N) content
of the cassava peels where found to be 9% and
34.7 which is a favourable condition for good
biogas production as reported by Manjula and
Mahanti (2014).
2.2
Experimental Set-Up And Procedure
In this experiment, rani bottle of 500 ml
capacities were used as bio-digesters or
reactors which were setup for the experiment
as shown on Plate 1. The effective working
volume of each bio-reactor is maintained at
200 ml and 300 ml left for the biogas. A
digital weighing balance was used to measure
the required mass of cattle dung and biomass
which were mixed in the ratio of 1:3 and water
was added to the mixture in the ratio of 1:3 by
volume. From the mixture, 200ml were put in
to each of the 9 digesters, on the covers of
each bottle small hole were provided to which
flexible connecting tube was attached. On the
other end of the flexible tube a rubber stopper
is attach to obtain a completely sealed
digestion chamber. When measuring the gas
production, a pressure gauge was attached to
the end of the flexible connection and then the
valves of the stoppers opened to measure the
pressure of the digestion chamber.
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Nigerian Journal of Tropical Engineering
Vol. 16 No. 1 |ISSN: 1595-5397| Dec. 2022
Jauro M. S. et al
DOI: 10.59081/njte.16.1.006
Where; 𝑉 = Volume of gas produced (m3)
𝑉𝐺 = Volume of the head space (m3)
∆𝑃 = Change in Pressure (pascal)
𝑃𝑎𝑡𝑚 = atmospheric pressure (pascal)
After every measurement of biogas
accumulation over time, the gas was allowed
to escape in order to avoid pressure build up
that would exceed pressure gauge capacity.
The average was recorded and reported as
biogas production.
3.0 Results and Discussion
The results of the chemical characteristics of
the cassava peels, chemical composition of the
biogas produced from the cassava peels and
the daily and cumulative volume of the biogas
produced are discussed in section 3.1, 3.2 and
3.3 respectively.
Plate 1: Batch Digester
To obtain replications for statistical purpose, 3
of the bottles containing the mixture were
placed into each of the 3 water bath and hot
water was added into the water bath until
when the temperature of each gets to the
required level as indicated by the thermometer
inserted into the water baths. To maintain
uniform temperature i.e. (35±50C, 45±50C and
55±50C) during the 30 days retention period of
the experiment within each the water bath, the
water baths are closed with a cover and a
mercury in glass thermometer passed through
a hole provided on them in to the digestion
unit for temperature measurement as well a
hole is provided on the water bath cover for
addition of hot water when the temperature
within the water bath goes down to rise the
temperature. The entire bio-digestion units
were agitated twice a day. Biogas produced
were measured using gas pressure gauge twice
a day for the first 7 days and then once a day
for the remaining 23 days of the experiment.
The measured pressure of the gas were
converted to volume of gas production per
kilogram total solid (m3/kg-TS) using the
relationship reported by Sofiane et al. (2013)
as presented in Equation (1)
𝑉 ∆𝑃
𝑉 = 𝑃𝐺
𝑎𝑡𝑚
3.1
Chemical characteristics of the
Cassava Peels
The chemical properties of the discarded
cassava peels as shown in Table 1 indicates
that the carbohydrate content of the cassava
peels is 61.92±0.02% which was found to be
very high compared to 32.49+0.5% obtained
for yam peels by Lawal et. al. (2014) as well
as 41.22 % obtained by Oparaku et. al. (2013)
for 50:50 blend of cassava peels and pig dug.
The total solid contain of the cassava peels
was found to be 9.0±1.0% which falls within
that of many agro-industrial waste reported by
Steffen et. al. (2004) but was found to be
lower than 67.86% reported by Oparaku et.
al. (2013) for 50:50 blend of cassava peels
with pig dug. The carbon to nitrogen ratio of
the peels was 32:1 which is a little higher than
the 30:1 recommended by Marchaim (1992) as
the optimum carbon to nitrogen ratio for biodigestion and lower than the 41:1 reported by
Oparaku et. al. (2013) for the blend of cassava
peels and pig dug in the ratio of 50:50. The pH
of the cassava peels was found to be between
6.8 % to 7.7% which fall within the optimum
... (1)
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Nigerian Journal of Tropical Engineering
Vol. 16 No. 1 |ISSN: 1595-5397| Dec. 2022
pH for bio-digestion recommended
Adelekan and Bamgboye (2009).
Jauro M. S. et al
by
DOI: 10.59081/njte.16.1.006
Olukanni (2022) for 1:1 ratio of cassava peels
to cow dung. The gas was found to also
contain minute quantity of Hydrogen Sulphide
similar to that reported by Fagbenle and
Olukanni (2022), Nitrogen and Hydrogen.
Table 2: Chemical composition of Biogas
Composition (%)
Table 1: Chemical composition of discarded
cassava peels
Characteristic
Composition
Total solid (TS) (%)
9.0
Volatile solids (VS) %
2.47
Carbon (C) (%)
13.1
Nitrogen (N) (%)
0.4
C: N Ratio
34.7
PH
7.3
EC (Ms/Cm)
12.6
B. O. D (mg/l)
11.3
C.O.D (mg/l)
20.6
Hemicellulose (%)
1.5
Moisture Content (%)
6.25
Ash (%)
11.51
Crude Lipid (%)
0.97
Crude protein (%)
3.11
Crude fibre (%)
16.2
Carbohydrate (%)
61.92
Constituents
Methane (Ch4)
Carbon Dioxide (Co2)
Hydrogen Sulphide (H2S)
Nitrogen (N2)
Hydrogen (H2)
3.3
Composition
67.0
38.7
1.1
0.4
0.4
Biogas production from Cassava
peels
at
various
Digestion
Temperatures
The daily and cumulative production of biogas
during the digestion of cassava peels at the
digestion temperatures of 35±50C, 45±50C and
55±50C are presented in Figures 1 and 2. From
Figure 1, it can be noted that gas production
begins on day 2 of the digestion for all the
three digestion temperature with a gas
production of 1.94 × 10−5 , 1.64 × 10−5 and
2.27 × 10−5 m3/kg-TS respectively. Similar
results were reported by Fagbenle and
Olukanni (2022); Ofoefule and Uzodinma,
(2009); Oparaku et. al. (2013) and Ismail et.
al. (2021). The highest daily yield of gas for
the three digestion temperature were on days
15 for the digestion temperature of 35±50C
and 45±50C with a production of 14.34 ×
10−5 and 13.32 × 10−5 m3/kg-TS which is
lower than day 12 reported by Fagbenle and
Olukanni (2022) for mesophilic temperature
digestion of cassava peels with cow dung in
ratio 1:1 but is similar to that of day 14
reported by Ofoefule and Uzodinma (2009)
and day 13 reported by Aisien and Aisien
(2020). While the peak gas production for the
55±50C digestion temperature was on day 10
with the production of 15.69 × 10−5 m3/kgTS.
The results indicated that cassava peels is a
suitable substrate for the Anaerobic Digestion
(AD) process as its chemical composition falls
within that reported by Fan et. al. (2008) as
suitable substrates for anaerobic digestion.
3.2
Chemical Composition of Biogas
from Cassava peels
The chemical composition of the biogas
produced from cassava peels is presented in
Table 2. The result shows that the gas contains
large quantity of Methane (CH4) of about
67.0% which is close to that of 65.1%
obtained by Adelekan and Bamgboye (2009)
for the blend of cassava peel and cattle but
lower than 33.6% reported by Fagbenle and
Olukanni (2022) for the blend of cassava peels
and cow dung mixed in the ratio of 1:1. The
result shows that the gas also contains 38.7%
Carbon dioxide which was found to be lower
than 64.1% reported by Fagbenle and
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Jauro M. S. et al
DOI: 10.59081/njte.16.1.006
the digestion temperatures of 35±50C, 45±50C
and 55±50C respectively.
After the peak production days the gas
production begins to decline to 0.23 × 10−5 ,
0.03 × 10−5 and 0.07 × 10−5 m3/kg-TS for
Figure1: Daily Biogas Production at different digestion temperature
The cumulative gas production for the period
of 30 days of the test is presented of figure 2.
A total of 289.33 × 10−5 m3/kg-TS was
produced when the digestion temperature was
55±50C, while 253.90 × 10−5 and 231.83 ×
10−5 m3/kg-TS were produced when the
digestion temperature were 35±50C and
45±50C respectively. Lower cumulative yield
of 0.6 l/kg-TS was reported by Adelekan and
Bamgboye (2009) for digestion of only
cassava peels which were increased to 13.7
l/kg-TS on mixing it with poultry waste, 35.0
l/kg-TS on mixing cassava peels with piggery
waste and 21.3 l/kg-TS on mixing it with cow
dung in the ratio of 1:1.
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Jauro M. S. et al
DOI: 10.59081/njte.16.1.006
Figure2: Cumulative Biogas Production at different digestion Temperature
4.0
Conclusions
From this study, it can be concluded that
biogas production from cassava peels mixed
with cattle dung can be improved by
increasing the digestion temperature as the 30
days cumulative biogas production increases
from 231.83 × 10−5 m3/kg-TS when the
mixture were digested at mesophilic
temperature range (35±50C) to 289.33 × 10−5
m3/kg-TS when digested at thermophilic
temperature range (55±50C), representing 25%
increase in gas production. So if we can
provide extra energy to increase the digestion
temperature, better and faster gas production
can be achieved from cassava peels. The only
disadvantage of the thermophilic anaerobic
digestion is that more energy has to be
expended to raise and maintain the
temperature from the mesophilic temperature
range to the thermophilic range.
Conflict of interest
The authors declared that there is no conflict
of interest in this work
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